1. Field of the Invention
Methods and apparatuses consistent with exemplary embodiments relate to an image forming apparatus and a method of controlling a developing unit thereof, and more particularly, to an image forming apparatus which compensates for an output value of a permeability sensor in a developing unit and controls toner supply, and a method of controlling a developing unit thereof.
2. Description of the Related Art
With the development of electronic technologies, various kinds of electronic apparatuses have been developed and distributed. Such electronic apparatus may display various contents and may be connected to an image forming apparatus to output the contents.
An image forming apparatus may be realized in various ways such as an ink jet method and a laser printing method. An image forming apparatus of the laser printing method may be divided into a 1-component developing method using only toners and a 2-component developing method using toners and carriers altogether.
The 1-component developing method is simple and is beneficial to miniaturization. In comparison to this method, the 2-component developing method is capable of developing at a high speed and shows good performance in reproducing gradation.
The 2-component developing method refers to a method that performs developing by mixing toners and carriers. The 2-component developing method should constantly maintain a concentration of toners in a developing agent. Accordingly, the image forming apparatus senses a toner concentration from a mixture of toners and carriers in a developing unit. As a result of sensing, if the toner concentration is low, more toners are supplied to the developing unit from a toner bottle, and, if the toner concentration is high, toner supply is restricted.
However, the toner concentration may be differently sensed according to a use time or a pause time of the image forming apparatus. Specifically, the image forming apparatus measures a quantity of electric charge of the mixture of the toners and the carriers contained in the developing unit, and senses the toner concentration according to the quantity of electric charge.
However, the quantity of electric charge in the developing unit may vary according to whether the image forming apparatus is used or not. For example, if the image forming apparatus is not used and is paused, a quantity of electric charge per unit mass decreases. In this case, the toner supply is controlled based on the decreased quantity of electric charge. Accordingly, the toners may be supplied excessively or insufficiently.
This may cause a problem that toners are scattered in the image forming apparatus or a problem that an image concentration is made non-uniform.